The present disclosure relates to a display input device including a display portion and a touch panel portion, a method of controlling the display input device, and an image forming apparatus including the display input device.
In recent years, equipment such as a multifunction peripheral, a copier, or a printer is equipped with an operation panel including a display portion and a touch panel portion. Using the touch panel portion, a touch position corresponding to a key or a button displayed on the display portion is recognized. A touch operation is accepted as an input of selecting a key or a button of a position corresponding to the touch position. When the input is accepted, a display on the display portion is changed (for example, the color of the button is changed). However, there is a case where the visual change is hard to recognize (particularly for a user having visual impairment). Therefore, in order to recognize that the touch is done (that the input of pressing the button is accepted) by the sense of touch, the touch panel portion may be vibrated.
There is known the following technique of vibrating the touch panel portion. Specifically, there is known an information display device including an information display surface, a transparent or translucent operation portion with a predetermined operation surface disposed on the information display surface, bidirectional functional means combined to the operation portion to be capable of converting between a mechanical action and an electric signal in a bidirectional manner, operation signal fetching means for fetching an electric signal generated from the bidirectional functional means by an operation force given to the operation surface as an operation signal, and drive control means configured to respond to the operation signal so as to send out an electric drive signal to the bidirectional functional means. By the drive signal, a mechanical reaction (vibration) generated in the bidirectional functional means is transmitted to the operation surface. With this structure, the operation surface is vibrated so that the user is provided with secure operation feeling.
As described above, by vibrating the touch panel portion, it is possible to recognize that the operation is accepted by the sense of touch.
In a cellular phone or the like, in order to vibrate the touch panel portion or a case, a vibration motor (for example, a motor with an eccentric weight attached to a rotor) may be conventionally used. However, in the case where the vibration motor is used, the vibration lasts for a relatively long period so that the operation feeling is deteriorated.
Therefore, a piezoelectric element may be used for vibrating (deforming) the touch panel portion. Utilizing characteristics of the piezoelectric element that deforms when a voltage is supplied, a voltage is supplied to the piezoelectric element as a pulse (as an impulse), for example, so as to vibrate the touch panel portion instantaneously (the vibration period of the touch panel portion is set to be shorter than in the case where the vibration motor is used). In this way, the user can be provided with operation feeling (click feeling) like that when a button or a key is pressed.
However, the display portion and the touch panel portion of the operation panel of the image forming apparatus such as the multifunction peripheral are much larger than those of the cellular phone. Therefore, in order to vibrate the touch panel portion of the image forming apparatus by the piezoelectric element, it is necessary to dispose a plurality of piezoelectric elements so that the user can be provided with operation feeling (click feeling) like that when a button or a key is pressed (so that the touch panel portion is sufficiently vibrated). For instance, the plurality of piezoelectric elements may be disposed along a long side direction of the touch panel portion or the display portion.
Here, when all the piezoelectric elements are simultaneously vibrated (when the piezoelectric elements are simultaneously deformed), vibrations of the piezoelectric elements may interfere with each other (cancel each other), and hence there may be generated a part with no vibration or a part with attenuated vibration in the touch panel portion. For instance, in a part sandwiched between the piezoelectric elements or in a part close to the piezoelectric element, vibration amount (deformation amount of the touch panel portion) is reduced. In this way, when a plurality of piezoelectric elements are used for vibrating the touch panel portion, there is a problem that the touch panel portion cannot be vibrated so as to provide the user with operation feeling (click feeling) like that when a button or a key is pressed.
Here, the technique described above is not a technique related to solution of the problem that the touch panel portion cannot be vibrated so as to provide click feeling when all the piezoelectric elements are simultaneously vibrated. Therefore, the technique described above cannot solve the above-mentioned problem.